To controllably run (move) an automated guided vehicle such as an automated guided stacker crane, an instruction value for position, speed, or acceleration needs to be provided to a motor (actuator) installed in the automated guided vehicle; the instruction value depends on a temporal variation in position, speed, or acceleration.
For example, where an instruction value for the speed is provided to the motor to run the automated guided vehicle over a given section, the corresponding speed pattern is normally set to draw a trapezoidal curve. The trapezoidal curve consists of three portions, an accelerated running portion (hypotenuse) in which the automated guided vehicle runs at a uniform acceleration, a uniform-speed portion (top side), and a decelerated running portion (hypotenuse) in which the automated guided vehicle runs at a uniform acceleration.
The Unexamined Japanese Patent Application Publication (Tokkai) No. 2002-32124 discloses an automated guided vehicle (rail guided carriage) for which a speed pattern is set to draw a trapezoidal curve.
To reduce vibration in the automated guided vehicle, an optimum control problem for maximizing vibration controllability may be solved to obtain a curve function corresponding to the optimum solution and used as a speed pattern for the automated guided vehicle. It is known that vibration can be effectively controlled by using the thus derived speed pattern (hereinafter referred to as an optimum speed pattern) to control the speed of the automated guided vehicle. This optimum speed pattern draws a complicated curve instead of the normal trapezoidal curve.
Further, although depending on what is to be optimized in the optimum control problem, where it is difficult to derive the optimum solution in the form of a continuous function, an approximate solution may be found every period of time t, that is, at given time intervals t, to derive the optimum speed V every period of time t. This results in dot-sequential data composed of dots P (t, V) where the elements of each dot are time t and speed V. The dot-sequential data forms an optimum speed pattern that is a continuous curve.
Where the optimum speed pattern is expressed by dot-sequential data, the dot-sequential data needs to be stored in a memory in the automated guided vehicle in order to run the automated guided vehicle in accordance with the optimum speed pattern. However, such dot-sequential data occupies a large space in the memory in the automated guided vehicle, the capacity of which must thus be increased in order to achieve the proper storage. For example, when instructions are given to the actuator such as a motor at the rate of one instruction per 1/1,000 sec., 1,000 data for each second needs to be pre-stored in the memory.
Furthermore, the optimum speed pattern varies depending on the distance that the automated guided vehicle runs or the position of center of gravity of the automated guided vehicle. For example, for a stacker crane, the distance that the stacker crane runs to transfer an article varies depending on the positional relationship between the source and destination of the article. Thus, to allow the same automated guided vehicle to run different distances, many dot-sequential data the number of which depends on the running distances needs to be stored in the memory in the automated guided vehicle. This further increases the amount of data to be stored in the memory.
Thus, a problem to be solved by the present invention is that when dot-sequential data indicating a temporal variation in position, speed, or acceleration is stored in the memory in the automated guided vehicle as it is, the capacity of the memory is insufficient and thus needs to be increased.